This invention generally relates to temperature controls and more particularly to a temperature control strategy that uses real time pricing information to provide an estimation of energy savings at selected times.
A variety of temperature control devices are commercially available to allow individuals to control the temperature within associated zones such as rooms, sections of a building or entire buildings. Over time thermostats have become more sophisticated and have included beneficial features. For example, programmable thermostats that allow an individual to set varying temperatures at varying times on a chosen schedule allow for more efficient energy use depending on the needs within the associated zone at particular times on a typical day.
In addition to the individual""s ability to set a schedule for varying temperatures, it has been proposed to permit an outside source, such as a utility company, to effectively reset an individual""s chosen set point temperature during a so-called curtailment period. The curtailment period would typically be utilized by a utility company to reduce the amount of energy consumption at strategic times.
Energy savings associated with such set point curtailments are calculated and posted on a regular monthly or similar billing cycle. Using such information, an individual can determine the amount of energy and associated cost savings achieved during set point curtailments.
There is a need for enhanced communication of energy savings information to an individual on a more individualized and readily available basis. This invention addresses that need in a unique fashion.
In general terms, this invention is a system and method for providing energy savings estimation information to an individual.
A system designed according to this invention includes a thermostat device that has a first input for selecting a first target temperature for the corresponding zone and a second input for changing the target temperature from the first target temperature to a second target temperature. The thermostat device also has a temperature sensor that provides information regarding an actual temperature in the zone. An estimator module gathers information regarding the actual temperature in the zone over a selected period of time when the system is set at one of the first or the second target temperature. The estimator module estimates a temperature in the zone over said selected period as if the system were set at the other of the first or second target temperature and provides an energy difference based upon a comparison between the actual temperature and the estimated temperature over said selected period.
The second input preferably is capable of receiving information from a second source remotely located from the thermostat device. The second input in one example communicates with a utility company so that the utility company can alter the target temperature for the zone during an energy usage curtailment period. In such an example, the estimator module provides an indication of the energy savings during the curtailment period. The estimator module preferably compares an actual temperature profile of the zone at the reset target temperature to an estimated temperature profile that indicates what the temperature would have been if the target temperature were not reset.
A method of this invention for determining an energy savings during a curtailment period where a target temperature for a selected zone is changed from a preselected target temperature includes several steps. An actual temperature in the zone is determined during the curtailment period with the changed target temperature. An estimated temperature in the zone during the curtailment period is determined as if the preselected target temperature were used during the curtailment period. A difference between the actual temperature and the estimated temperature over the curtailment period is then determined. An amount of energy saved is determined based upon the determined difference between the actual temperature and the estimated temperature over the curtailment period.
In one example, the rate of heat flow carried by supply air into the zone, a thermal capacitance of the air in the zone and a thermal resistance of the walls separating the zone from unconditioned air are used to determine the estimated temperature in the zone during the curtailment period as if the preselected target temperature were used. An equilibrium condition for the zone preferably is determined during the time period when the target temperature is the preselected target temperature. The equilibrium condition information is then used to determine the rate of heat flow carried by the supply air into the zone, the thermal capacitance of the air in the zone and the thermal resistance of the walls. This information is then used when estimating the temperature in the zone during the curtailment period as if the preselected target temperature were used during the curtailment period instead of the changed target temperature.